This invention relates to a power supply apparatus, for example, a power supply apparatus for use with, for example, a welder.
There are various welding techniques, such as manual welding and TIG welding. A power supply apparatus suitable for a particular welding technique is selected.
A general description of the basic structure of power supply apparatuses for welders is given hereunder. A commercial AC voltage is converted to a DC voltage by an input-side rectifier and a smoothing capacitor of a power supply apparatus. The DC voltage is converted to a high-frequency voltage in an inverter, which, in turn, is transformed to a desired voltage in a transformer. The resulting voltage is converted back to a DC voltage in an output-side rectifier for application to a load. If necessary, this ultimate DC voltage may be converted to a low-frequency AC voltage before it is applied to a load. By virtue of the use of an inverter for converting a DC voltage to a high-frequency voltage, this type of power supply apparatus can use a small-sized transformer, which results in downsizing of the power supply apparatus itself.
A power supply apparatus for use in manual welding with the above-described basic configuration has a constant-current output characteristic, in which a constant output current is provided even when its output voltage varies. The power supply apparatus is provided with a control panel on which an output current setter for setting the value of the output current is disposed.
In manual welding, when the welding is to be initiated or when, for example, a load including a welding torch and a workpiece is short-circuited, hot-starting of the welder may be employed for generating a desired arc by supplying to the load with current larger than the output current. A hot-start setter for setting the current to be supplied for hot-starting of the power supply apparatus is also disposed on the control panel. Indicators for indicating the magnitudes of the output voltage and current are also disposed on the control panel.
DC TIG welding is suitable for, for example, welding stainless steel, and a power supply apparatus for use in DC TIG welding has a constant-current output characteristic. DC TIG welding sometimes requires hot-starting as in manual welding. When DC TIG welding is employed for welding a flat workpiece, the output current value is held constant. On the other hand, when DC TIG welding is used for welding a workpiece like a pipe, a pulse output current is used. When a pipe, in particular its bottom portion, is welded with a constant output current, melt may drop from the pipe, which may necessitate another welding. Sometimes, melt may adhere to a TIG welding electrode of the torch and damage the electrode. By applying pulse current instead of a constant current, a molten weld pool formed in the bottom portion of the pipe is cooled down while a base portion IB of the pulse current is flowing, to thereby prevent the melt from dropping from the pool or adhering to the torch welding electrode.
There are two methods for initiating arcing in DC TIG welding. One is a touch-starting method in which a small current is supplied to the welding electrode with the electrode and the workpiece short-circuited, and, after that, the electrode is separated from the workpiece to thereby generate an arc between them. The other method is a high-frequency starting method, in which the welding electrode is kept separated from the workpiece, and a high-frequency, high voltage, which may have a frequency of from, for example, 1 MHz to 3 MHz and a magnitude of from, for example, 5 kV to 20 kV, is applied between them to thereby initiate arcing.
The power supply apparatus for DC TIG welding may be provided with a control panel with an output current setter and a hot-start setter disposed thereon. In addition to these setters, disposed on the control panel are up-ramping and down-ramping time setters for use when a pulse current is applied as an output current. The up-ramping time setter is for setting an up-ramping time during which a starting current increases to a maximum pulse current (i.e. a set output current), and the down-ramping time setter is used to set a down-ramping time during which the current decreases from the maximum pulse current value to the value of a crater current which is caused to flow at the end of the welding. Also disposed on the control panel are a pulse frequency setter for setting the frequency of the pulse current, a pulse current switch for switching the current to be supplied to the load between a DC current and a pulse current, an arc-initiating mode switch for switching the arc-initiating mode between the touch-starting mode and the high-frequency starting mode, and indicators for indicating the values of the output voltage and output current.
AC TIG welding is used for welding, for example, an aluminum material. An aluminum workpiece has an oxide film thereon having a high melting point. Therefore, if a DC power supply is used and current is supplied with a workpiece serving as a positive electrode and with a welding electrode serving as a negative electrode, the workpiece cannot be heated to a temperature high enough for welding. Accordingly, the workpiece is made a negative electrode with the welding electrode made to act as a positive electrode, thermoelectrons are emitted from the workpiece when current is supplied, which removes the surface oxide films, enabling the welding. The removal of oxide films is called xe2x80x9ccleaning effectxe2x80x9d. On the other hand, when the workpiece is used as a positive electrode with the welding electrode made to act as a negative electrode, the electrode can be cooled. Accordingly, when AC TIG welding is used, both the cleaning effect and the cooling effect are available. By adjusting the time periods during which the workpiece is serving as a positive electrode and a negative electrode, the amounts of the cleaning and cooling effects can be adjusted.
An AC/DC TIG welder can be used both for AC TIG welding and DC TIG welding. On a control panel of a power supply apparatus for an AC/DC TIG welder, there are disposed an output current setter, a hot-start setter, an up-ramping and down-ramping time setters, a pulse frequency setter, a pulse current switch for switching supplied current between a DC current and a pulse current, an arc-initiating mode switch for switching the arc-initiating mode between the touch-starting mode and the high-frequency starting mode, and indicators for indicating the values of the output voltage and output current for DC TIG welding. In addition, there are disposed a voltage-frequency setter for setting the frequency of the voltage for the AC welding, a waveform balancer for setting the ratio between positive and negative portions of the pulse current.
Because of various setting devices put on control panels of power supply apparatuses for welders, as described above, various different procedures are required for manufacturing power supply apparatuses for various welding methods. Also, it requires complicated arrangements to manufacture a single power supply apparatus which can be used for various welding modes or techniques because of a number of setting devices. In addition, settings using such various setting devices will be very troublesome.
In Japanese Patent No. 3,231,694 issued on Sep. 14, 2001, or in corresponding U.S. Pat. No. 6,051,806 assigned to the same assignee of the present application, a power supply apparatus is disclosed, which includes a control panel. On the control panel, there are provided a welding mode selection push button with which a welding mode, e.g. manual welding or DC TIG welding, is selected, a parameter setting push button with which a parameter for the selected welding is set, and one setter with which output current, output voltage etc. are set for the selected welding mode. In addition, a welding mode indicator, a parameter indicator, an UP/DOWN push button for changing the set parameter, an output voltage indicator and an output current indicator.
Since power supply apparatuses are used not only indoors but also outdoors, they have to be protected from water drops and dust. For that purpose, a control panel of such power supply apparatuses may be provided with a water-proofing or dust-proofing cover. When an operator wants to use the power supply apparatus with a water-proofing panel cover, the operator has to remove the cover in order to set the welding mode, the parameter and the output voltage and current, which hinders prompt setting operations.
An object of the present invention is to provide a power supply apparatus which enables an operator to set various settings easily and promptly.
According to an embodiment of the present invention, a power supply apparatus includes a case with a control panel. A plurality of controllers are disposed on the control panel. The controllers may be for selectively setting operating modes, and various parameters. A cover is put on the control panel. The cover is desirably water and dust proofing. At least one of the controllers is externally operable so that it can be operated even when the cover is closed. For example, the externally operable controller may have a tip end extending outward through and beyond the cover. The externally operable controllers may be any controllers, but they are desirably controllers operated frequently.
The power supply apparatus according to the present invention may be used for welding and is operable in a desired one of a plurality of operating modes, such as a manual welding mode, a DC TIG welding mode and an AC TIG welding mode, for example. In this case, a parameter setting controller for use in setting a parameter for a selected mode may be an externally operable controller, so that there is no need for an operator to take the trouble to open the cover in order to change the parameter.
The externally operable controller may be arranged to be placed in a parameter setting mode when it is pressed. In the parameter setting mode, the externally operable controller can set a parameter by being rotated or slid. With this arrangement, even if an operator erroneously operate or rotate or slide the externally operable controller without first pressing it into the parameter setting mode, inadvertent change of the already set parameter can be prevented.
The cover may extend from one end to the other of the control panel with one end of the panel supported by a rotation shaft so that the cover can rotate about a rotation shaft The cover is provided with an opening. The opening is so positioned that when the cover is put over the control panel, the externally operable controller extends through it and a controller operating tip, e.g. knob of the externally operable controller can be outside the cover. The opening in the cover is arranged such that, when the cover is rotated open about the rotating shaft, the operating tip of the controller comes out of the opening. With this arrangement, the externally operable controller can be operated even when the cover is closed, and the controller does not interfere with the cover when it is rotated open.
According to another embodiment of the present invention, a power supply apparatus includes a case with a control panel. A plurality of controllers for setting characteristics of power supply circuitry housed in the case are disposed on the control panel. A cover is provided for the control panel. The cover, in its closed position, has at least part of each of the two side edges substantially contacting the case, and is mounted, at the contacting parts, to the case in such a manner as to be rotatable about an axis extending substantially perpendicularly to the side edges. For example, rotating shafts may be provided to extend along the rotation axis from the respective side edges of the cover. The rotating shafts are rotatably received by corresponding bearings formed on the case. On the other hand, rotating shafts may be provided to extend along the rotation axis from the case toward the cover which has holes for receiving the rotating shafts.
At least one protuberance is formed in either the side edges of the cover or the case on a circumference of a circle centered about the rotation axis. A plurality of protuberances may be formed along the circle at regular intervals. A plurality of recesses are formed in the other of the side edges of the cover and the case along the circumference of a corresponding circle centered about the rotation axis. The recesses are so positioned as to be able to receive the protuberance. The protuberance is adapted to be received in one of the recesses when the cover is closed, and, as the cover is opened wider, the protuberance moves to extend into successive ones of the recesses. When the cover is opened to a desired extent, it can keep its position since the protuberance engages with one of the recesses. Since the cover need not be held by hand, the operation of the controllers is easy.
A cable may be led into the case through a lead-in hole formed in the case. A first clamping member is formed integral with the case at a portion around the lead-in hole. The first clamping member is adapted to surround an approximately half of the circumference of the cable. A second clamping member is adapted to surround the remaining part of the circumference of the cable. The second clamping member can be secured to the first clamping member with the cable disposed therebetween, whereby the cable can be clamped easily.
The case may include front and rear case sections and an intermediate case section contacting and connecting the front and rear case sections. Circuit components of the power supply apparatus are disposed in the intermediate case section, and a water-proofing sheet is placed in the intermediate case section to cover the circuit components. The sheet includes a first flap extending from a portion of an upper part of the sheet into the front case section, and a second flap extending from a portion of the upper portion of the sheet into the rear case section.
With this arrangement, even if water, for example, rain, goes into the interior of the power supply apparatus through the abutment between, for example, the front and intermediate case sections, the water will flow over the first flap of the water-proofing sheet, and, therefore, the circuit components disposed inside the sheet will not be damaged by the water. The same thing can be said when water goes into the case through the abutment between the rear and intermediate case sections.
A first protrusion may be formed in one of the abutting end surfaces of the front and intermediate case sections, with a corresponding first recess formed in the other of the abutting end surfaces, and a second protrusion may be formed in one of the abutting end surfaces of the rear and intermediate case sections, with a corresponding second recess formed in the other of the abutting end surfaces. The first protrusion is arranged to be received in the first recess, while the second protrusion is arranged to be received in the second recess. When the front, intermediate and rear case sections are assembled, the first and second protrusions enter into the corresponding first and second recesses, and, therefore, the front, rear and intermediate case sections can be secured firmly together and will not be displaced.